The laser system in our experiments consists of a Nd:YAG oscillator and three Nd:glass amplifiers with diffraction-limited output beams. Crystals for frequency doubling are KDP and KD*P. When unfocused collimated laser beams were used in frequency doubling, a maximum energy, conversion efficiency of 65% has been obtained,the corresponding peak power conversion efficiency was about 84%. In the case of low laser power, by means of cylindrical focusing laser beams, energy conversion efficiencies were increased by a factor of 8 to 30 with a maximum conversion efficiency of 64%.